Adjusted efficiency: Raw offensive efficiency is points scored per 100 offensive possessions. The adjusted version adjusts for the quality of opposing defenses, the site of each game, and when each game was played (recent games get more weight). Defensive efficiency is points allowed per 100 defensive possessions, adjusted for the same things. (The ratings glossary page has more details on points per possession calculations.)

Tempo: We can estimate possessions very well from box score stats by using this formula: FGA-OR+TO+0.475xFTA.
For each team, possessions are counted for the team and their opponents, and then averaged. A team’s average tempo is total possessions divided by minutes. This value is then adjusted for schedule, considering the preferred pace of each opponent and when each game was played